Imagine a search engine that simply removed the top 1 million most popular web sites from its index. What would you discover?
A mix of affiliate-driven content sites, abandoned blogs & spam sites, based on some of the searches I did. The broader the category, the more likely I think you are to stumble on something relevant and helpful.
(Also, .gov sites don't seem to have been removed from the index. A search for "type 2 diabetes" still brings a number of results from NIH.gov, mimicking what Google serves up.)